Returns the current execution stack—an array containing strings in the form file:line or file:line: in `method’. The optional start parameter determines the number of initial stack entries to omit from the top of the stack. A second optional length parameter can be used to limit how many entries are returned from the stack. […]

belongs_to relationships will be required by default (the parent resource must exist in order for the child to be valid). You can make the parent resource optional by passing :required => false as an option to belongs_to.

WordPress: pre_get_posts filter to display one post per category. Displays the latest sticky post and therefore excludes the category of the sticky post as we only want one post per category. By: Silvan Hagen